Very nice performance; you could surely do 100 now. If you want to progress beyond 100 miles, I would suggest brevet riding. Check out RUSA or the long distance forum for more info. Brevets are timed, but non-competitive events. For example, you get a 13+1/2 hour time to complete 200k (@125 miles), 20 hours to go 300k (@200 miles), etc. It sounds like you have the will to do it. Best of luck at 100 and beyond.